This invention is in the field of watermelon breeding, specifically relating to diploid watermelons used to pollinate triploid watermelon plants for the commercial production of seedless watermelon fruit, and includes a novel method for the production of triploid watermelon fruit.
Watermelon is an important horticultural crop that accounts for 2% of the world area devoted to vegetable crops. There were 6,024,000 acres of watermelon grown in the world and 187,000 acres of watermelons grown in the United States in 1997 (FAO Production Yearbook 51, 1998). The estimated annual world watermelon value exceeded $7.6 billion when using the United States average price for 1995-1997. The United States watermelon crop amounted to over 41 million cwt, from over 174,000 harvested acres, and a farm value of over $266 million, accounted for 9.2% of the harvested acres, 10.0% of the production, and 3.5% of the value of the United States fresh vegetable industry in 1999 (USDA Agricultural Statistics 2001). California was the leading state in watermelon farm gate value, exceeded $72 million 2000, due to high percentage of triploid seedless watermelon grown in California Seedless watermelon receives well above the average price for seeded watermelons in the market.
The goal of plant breeding is to combine in a single variety or hybrid various desirable traits. Desirable traits may include resistance to diseases and insects, tolerance to heat and drought, reducing the time to crop maturity, greater yield, and better agronomic quality. With mechanical harvesting of many crops, uniformity of plant characteristics such as germination and stand establishment, growth rate, and maturity, are important. Other desired traits may include particular nutrient content, color, fruit shape, as well as taste characteristics.
As with many different plants, watermelon contains a fruit part and a plant part. Each part contains different traits that are desired by consumers and/or growers, including such traits as flavor, texture, disease resistance, and appearance traits such as shape and color. The seedless trait in the watermelon fruit is highly desired by consumers. For production of seedless watermelon, optimum pollination characteristics of the pollinating plant are desired.
Seedless watermelon plants are triploid and must be pollinated by the pollen of diploid watermelon plants. To provide adequate pollenization of seedless watermelon plants, it is current practice to plant diploid pollenizer plants over approximately 25-33% of the field surface. The remaining portion of the field is planted with the triploid plants. Thus, to maximize the value of the crop in the field, growers use high yield marketable diploid watermelon varieties, which ultimately compete with the triploid seedless varieties for sun, nutrients, and space. The present invention recognizes the need to increase the pollenizing capacity of diploid watermelon plants in order to decrease the ratio of diploid to triploid plants in the field, thereby increasing the yield of the seedless watermelon. The present invention further recognizes that the novel phenotypic characteristics of the diploid pollenizer plants of the invention permits these diploids to be planted in close proximity to the triploid plants and to share the field surface with the triploid plants, thereby effectively decreasing the surface area of the field required for the diploid pollenizers of the invention.
The present invention uses a novel diploid watermelon to improve current methods of commercial production of seedless watermelon and to increase seedless watermelon yield. According to the invention, there is provided a novel enhanced, pollenizer diploid watermelon (hereinafter referred to as xe2x80x9cenhanced pollenizerxe2x80x9d) and method for pollinating seedless watermelon plants. The present invention includes an enhanced pollenizer having a high number of open (lacy) branches. The openness of the branched or lacy vine results, in part, from the distinct small and non-overlapping, deep lobed leaves. The lacy branches and small, non-overlapping, deep lobed leaves of the invention provide more access of bees to the flowers of both the pollenizing and the triploid plant, thereby enhancing transfer of the pollen from enhanced pollenizer watermelon to the female flowers of the triploid watermelon. A second advantage of small leaves characterized by deep, non-overlapping lobes is that more sunlight is able to penetrate to adjacent triploid plants. The third advantage of small leaves characterized by deep, non-overlapping lobes is that these leaves take up less field area than the substantially larger leaves of the diploid pollenizers currently used in the production of seedless watermelon.
Also according to the present invention, there is provided a novel enhanced pollenizer comprising small fruits with brittle rind. The small fruits with brittle rind reduce the load to the plant and allow the plant to continue flowering for extended periods of time, significantly greater than pollenizer watermelons that are currently used in the production of seedless watermelon. Longer flowering duration of the enhanced pollenizer, compared to traditional pollenizer diploid watermelons, results in increased fruit set and yield of seedless watermelon.
The present invention also includes an enhanced pollenizer fruit that weighs approximately in the range of 2 to 7 lbs.
The present invention further includes an enhanced pollenizer fruit rind that breaks under a pressure approximately in the range of 7-11 lbs/in2.
The present invention includes an enhanced pollenizer having leaves with a surface area approximately in the range of 25-40 cm2.
Also included in the invention is a enhanced pollenizer plant for pollinating triploid plants producing seedless watermelon fruit, comprising, at maturity, the characteristics of smaller fruit and leaf size compared to the watermelon variety Sangria(trademark), deep, non-overlapping lobes, wherein the fruit rind is more brittle than the rind of the variety Sangria(trademark).
The pollenizer diploid watermelon of the invention is further enhanced by including resistance to various pests and herbicides via conventional plant breeding methods or genetic transformation.
The present invention also provides a method for inter-planting enhanced pollenizer plants amongst the triploid watermelon plants in a field in a pattern that decreases the ratio of pollenizing plants to triploid plants and increases the field surface for triploid plants.
Also included in the present invention is a method of increasing the yield of triploid, seedless watermelon comprising the steps of reducing fruit load of said enhanced pollenizer watermelon, increasing the flowering duration of said pollenizer watermelon, planting said enhanced pollenizer watermelon in a field of triploid watermelon; and harvesting said triploid watermelon.
The invention also a method of increasing the yield of triploid seedless watermelon plants by using small fruited, yet enhanced pollenizer watermelon plants wherein the fruit are not harvested for human consumption.